NEW YORK--What should have been good news for a woman whose family had a history of breast cancer--that she did not carry the breast cancer gene (BRCA1)--proved bittersweet, since the woman had had bilateral prophylactic mastectomies 5 years earlier.
"This woman had a hard time deciding whether she wanted to know her results," said Barbara Weber, MD, associate professor of medicine and genetics and director, breast cancer program, University of Pennsylvania School of Medicine, Philadelphia.
The story points out the perils of genetic testing and the need for women to receive professional counseling about their risk, as well as prophylactic options if the test is positive, Dr. Weber said at the American Society of Breast Disease and New York Metropolitan Breast Cancer Group meeting.
"We tend to use cumulative risk in counseling women," she said. "We can tell a woman who carries the BRCA1 mutation that her risk of getting breast cancer by the time she is 40 is 15%; by age 50, 60%; by age 60, 70%; and by age 80, 85%. . . . That gives women a much better idea of what their risk actually is over a certain time period."
Although a woman carrying a BRCA1 mutation has an 87% lifetime cumulative risk of breast cancer, if she is from a high-risk family but did not inherit the mutation, her risk is closer to 11%, the general population risk. "In fact, it may be even lower than that," Dr. Weber said, "because the 11% risk calculation includes all women with a family history."
Thus, counseling women from inherited breast cancer families is difficult, because "either they inherited the mutation, and their risk is very high, or they didn't, and their risk is very low," she said. In addition, more than half of the risk in the women who carry the mutation occurs before the age of 50.
Many of these women mistakenly think that their risk is 50%. "Their risk of inheriting the mutation that predisposes them to breast cancer may be 50%, but within these families, virtually nobody's risk appears to be 50%," Dr. Weber said.